Elements of electricity, magnetism, and electro-magnetism : embracing the late discoveries and improvements : digested into the form of a treatise, being the second part of a course of natural philosophy : compiled for the use of the students of the University at Cambridge, New England / by John Farrar.

  • Farrar, John, 1779-1853.
Date:
1826
Catalogue details

Licence: Public Domain Mark

Credit: Elements of electricity, magnetism, and electro-magnetism : embracing the late discoveries and improvements : digested into the form of a treatise, being the second part of a course of natural philosophy : compiled for the use of the students of the University at Cambridge, New England / by John Farrar. Source: Wellcome Collection.

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

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    menls, w illi which we shall become acquainted as we proceed, and by means of which we shall be able to comprehend the most delicate phenomena; but the one above described will an- swer our purpose for the present. By subjecting to this proof a great variety of bodies, rubbed with diflerent substances, we shall find that there is no constancy as to the kind of electricity developed, but that this depends as much on the nature of the rubbing substance, as on that of the body rubbed. Polished glass, for example, rubbed with woollen, acquires, as we have before said, the vitreous electricity; but when rubbed with a cat skin, it takes the resinous electricity. Silk rubbed with resin, exhibits the resinous electricity; rubbed with polished glass, it acquires the vitreous electricity. The several substances of the subjoined table take the vitre- ous electricity when rubbed respectively with the substance immediately following; and the resinous when rubbed with that which precedes; Cat skin. Paper, Polished glass, Silk, Woolen cloth, Gum lac, Feathers, Rough glass, Wood. It will hence be seen, that there is apparently no connection between the nature of the substance and the kind of electricity produced by it. The only general law which is known to exist among these phenomena, is, that the rubbing body and the body rubbed ahoays take different electricities ; if the one be resinous, the other is vitreous, and vice versa. To ascertain this in any particular case, w^e must insulate the two bodies which are to be rubbed against each other. If they are solid, we fit to them handles of glass or resin, by which they may be held. It is well when it is possible, to give to the substances rubbed the form of plates, that the friction may take place over a greater surface. We may insulate and try in the same Avay a solid body and pieces of cloth, fur,&;c., or two substances of the latter kind only, &c. When we have continued the fric- tion for a short time, we separate the two bodies; and holding